Conventionally, as a power conversion apparatus being configured by a semiconductor switch module, which can bidirectionally supply a power, and a snubber circuit for suppressing a surge voltage, a circuit configuration such as shown in FIG. 3 is known. (For example, see Patent Reference 1 or Japanese Patent Application No. 2002-137871.)
The snubber circuit is configured by: snubber diodes D1 to D12; a snubber capacitor 40; and a snubber discharge circuit 30, and suppresses a surge voltage which is generated in switching of a semiconductor switching device, thereby preventing the semiconductor switching device from being broken down. The semiconductor switch module 20 is configured by eighteen high-reverse breakdown voltage IGBTs (Insulated Gate Bipolar Transistors) 501 to 5018 which are semiconductor switching devices having a self arc-extinguishing ability and a reverse withstand characteristic, so that a power can be bidirectionally supplied between input terminals 201 and output terminals 202.
In the semiconductor switch module 20, two of the eighteen high-reverse breakdown voltage IGBTs 501 to 5018 are connected in antiparallel to each other to constitute one bidirectional switch, thereby constituting nine bidirectional switches. Three bidirectional switch groups each configured by three bidirectional switches are connected to the three input terminals 201 and one of the three output terminals 202, respectively.
In the snubber circuit, a clamped snubber circuit is formed by the snubber diodes D1 to D12 which are high-speed diodes having an excellent reverse recovery characteristic, at the input terminals 201 and output terminals 202 (R, S, T, U, V, W) of the semiconductor switch module 20, and both ends of the clamped snubber circuit are connected to the snubber capacitor 40 which stores an absorbed surge voltage. Sometimes, the snubber discharge circuit 30 for discharging when the voltage of the snubber capacitor 40 is raised is further disposed.
FIG. 4 shows the appearance of the semiconductor switch module 20 shown in FIG. 3. In the semiconductor switch module 20 shown in FIG. 4, the eighteen high-reverse breakdown voltage IGBTs 501 to 5018 are enclosed in a resin mold 200. In the semiconductor switch module 20, the input terminals 201, the output terminals 202, mounting holes 203, and semiconductor switch driving gate terminals 204 are configured so as to be exposed to the outside of the resin mold 200. The semiconductor switch driving gate terminals 204 are connected to gate terminals of the high-reverse breakdown voltage IGBTs 501 to 5018, respectively, and a control signal is connected to the semiconductor switch driving gate terminals 204 to control the switching operations of the high-reverse breakdown voltage IGBTs 501 to 5018.
For example, the snubber diode D1 has a shape as shown in FIG. 5, and an anode terminal A1 and a cathode terminal K1 have a thread shape. A snubber circuit using such discrete snubber diodes is configured as shown in FIG. 6. More specifically, the anode terminals A1 and cathode terminals K1 of the snubber diodes having the configuration shown in FIG. 5 are connected to one other to form serial diodes, lead wires are drawn out from connections of the anode terminals A1 and the cathode terminals K1 in the serial diodes, and the lead wires are connected to the input and output terminals 201, 202 of the semiconductor switch module 20. Among ends of the serial diodes, the cathode terminals K1 are connected to P-side bus bars 1, 2, and the other terminals, or the anode terminals A1 are connected to N-side bus bars 3, 4. The P-side bus bars 1, 2, and the N-side bus bars 3, 4 are connected to the snubber capacitor 40 through P-side lead wires 103, and N-side lead wires 104.
[Patent Reference 1]
JP-A-11-146649